As it is known, conveyor belts are mechanical devices having the function of moving, continuously or from point to point, semi-finished or finished goods (arranged in bulk or in an orderly fashion) along production lines, for example to feed/load products in a production line, to transfer them from one workstation to the next, or to unload/store finished products.
Conveyor belts typically consist of a frame or metal structure comprising the support of the belt (the sliding surface or the supporting rollers), a drive pulley or roller (typically the head pulley) and a guide pulley or roller (typically the tail pulley) with idle rotation and a belt made of canvas or impregnated canvas or rubber or rubberized canvas, or a mesh made of plastic, steel or of another known and suitable material on which the products or semi-finished goods are placed and conveyed, in a more or less orderly fashion, during the production or storage cycle or the like.
Conveyor belts can have, according to the specific requirements for movement of the products or to the type of products to be moved or the layout of the system in which the conveyor belt is installed, a flat rectilinear development or can follow curvilinear paths or even have an inclined development.
In particular, the conveyor belt with inclined or sloping development is used in the case of transporting/conveying material from a lower to a higher level, or vice versa.
A conveyor belt with a structure of this type can consist of an integrated and rigid structure comprising, for example, two horizontal portions arranged on different levels, rigidly and stably connected to each other by means of an intermediate portion sloping with the inclination of the sloping portion calculated in the design stage as a function of the requirements.
However, this solution has some problems linked to the fact of having to accurately calculate the slope of the belt in the design stage and, moreover, does not allow re-use of the conveyor belt if different inclinations are required: in fact, this conveyor belt is made to measure for a specific system.
According to other conventional embodiments, the sloping conveyor belt structure can be of modular type with a sloping module arranged between belt modules positioned according to horizontal surfaces at different levels; for example, by varying the type of sloping intermediate module or the difference in level between the flat modules it is possible to reconfigure the system.
Although these solutions are advantageous with respect to those with fixed slope described previously, they still have some noteworthy problems linked to the fact that the single modules must each be provided with a proper motor, with consequent complications as regards control of the modules (in terms of conveyor belt speed) thus coupled and correct synchronism between them.
To solve these problems elevator conveyor belts have been developed in which the slope of the portion intermediate to the two horizontal portions can be changed using a lever mechanisms, devices of the rack and pinion type, idle and return rollers for the reciprocally sliding movement of plates.
One solution that solves the problems above is, for example, described in EP0731040, in which the conveyor belt comprises a supporting frame on which a sliding belt is wound, said frame comprising at least two portions hinged to one another for adjustment of the reciprocal angular position so as to go from a sloped configuration (with one ascending portion or one descending portion) to a configuration in which said two portions lie on a same horizontal plane and in which, to maintain the tension of the conveyor belt constant when the configuration is changed, one of the portions of the frame comprises, in correspondence of the unconstrained ends, a flange that slides longitudinally inside the frame suitable for changing the longitudinal distance between the ends of the conveyor belt and optionally provided with a preloaded spring for elastic return.
Another solution is described in the document FR2956103, in which adjustment of the angular position is implemented by means of a ramp provided with rollers or similar sliding means and arranged in correspondence of the hinge connection between the portions of the frame, with one end hinged with respect to a portion of frame and with the other opposite end sliding in a slot of the adjacent portion of frame, while adjustment of the tension of the conveyor belt when the relative angular position between said portions is changed is obtained by means of guide rollers on which the conveyor belt is tensioned and which move with respect to the longitudinal direction of advance of the same belt.
However, although these construction solutions effectively solve the problem linked to the change of the slope of the intermediate portion of the elevator and to control of the movement, they have some noteworthy problems linked to the complexity of their construction (for example, large number of components) and design and, consequently, to the resulting correlated costs.
A further drawback is linked to the fact that in these known conveyor belts with adjustable slope, while sliding along portions with different inclinations/slopes, the belt tends to form “bulges”, i.e. local deformations of the belt, which can prevent correct and uniform sliding of the belt and, consequently, correct movement of the material on the same belt.